Modulated light source

ABSTRACT

A method of producing a modulated light source including the steps of providing a modulator, fiberlessly coupling a laser diode light source to the modulator and enclosing the modulator and the laser diode light source within a housing together with output optics operative to direct modulated light from the modulator into an optical fiber extending outwardly from the housing.

This is a continuation, of application Ser. No. 09/312,781, filed May17, 1999 now U.S. Pat. No. 6,304,695. Each of these prior applicationsis hereby incorporated herein by reference, in its entirety.

FIELD OF THE INVENTION

The present invention relates to light modulators generally.

BACKGROUND OF THE INVENTION

Various types of light modulators are known. These include, for example,Mach-Zehnder type modulators and electroabsorption modulators. Thefollowing literature references describe various Mach-Zehnder typemodulators:

High-Speed Electrooptic Modulation in GaAs/GaAlAs Waveguide Devices, byRobert G. Walker, Journal of Lightwave Technology, Vol LT-5, No. 10, pp1444-1453, October, 1987 and the references therein;

Broadband Y-branch electro-optic GaAs waveguide interferometer for 1.3micrometers, by P. Buchmann et al, Applied Physics Letters, Vol 46, No.5, pp 462-464 (1985);

Broad-Band Guided-Wave Electrooptic Modulators, by Richard A. Becker,The Journal of Quantum Electronics, Vol. QE-20, No. 7, July, 1984, pp723-727;

The following product publications describe what is believed to be thestate Mach-Zehnder optical modulators:

LC100 Series GaAs Optical Modulators for D.C. to 50 GHz, GEC-Marconi,Materials Technology, Caswell Towcester, Northamptonshire, U.K.

2.5 GHz, 8 & 18 GHz Integrated Optical Amplitude Modulators, GECAdvanced Optical Products, West Hanningfield Road, Great Baddow,Chelmsford, Essex, U.K.

The following reference shows an optical switch which employs amultimode interference coupler:

Novel 1×N and N×N integrated optical switches using self-imagingmultimode GaAs/AlGaAs waveguides by R. M. Jenkins et al., AppliedPhysics Letters, Vol 64 (6), Feb. 7, 1994, pp. 684-686.

SUMMARY OF THE INVENTION

The present invention seeks to provide an improved and exceedingly costeffective optical coupler.

There is thus provided in accordance with a preferred embodiment of thepresent invention a modulated light source module including a modulatordisposed in a housing, a laser diode light source disposed in thehousing and fiberlessly coupled to the modulator, and output opticsoperative to direct modulated light from the modulator into an opticalfiber extending outwardly from the housing.

Further in accordance with a preferred embodiment of the presentinvention the modulator includes an input multi-mode interferencecoupler; an output multi-mode interference coupler, and first and secondwaveguides interconnecting the input multimode interference coupler andthe output multi-mode interference coupler, the first and secondwaveguides having associated therewith electrodes for the application ofvoltage thereacross, thereby to vary the phase of light passingtherealong.

Still further in accordance with a preferred embodiment of the presentinvention the modulator includes an input Y-junction splitter, an outputY-junction combiner, and first and second waveguides interconnecting theY-junction splitter and the output Y-junction combiner, the first andsecond waveguides having associated therewith electrodes for theapplication of voltage thereacross, thereby to vary the phase of lightpassing therealong.

Additionally in accordance with a preferred embodiment of the presentinvention the laser diode light source is monolithically integrated withthe modulator.

Preferably the laser diode light source is monolithically integratedwith the modulator and occupy different regions of at least some ofidentical epitaxial layers.

Additionally or alternatively in accordance with a preferred embodimentof the present invention the laser diode light source is a discreteelement which is mechanically mounted in a desired position with respectto said modulator.

Still further in accordance with a preferred embodiment of the presentinvention the laser diode light source is butted against an input to themodulator.

Alternatively the laser diode light source is coupled to an input to themodulator via a discrete lens.

Additionally in accordance with a preferred embodiment of the presentinvention the each of the laser diode light source and the modulator aremounted on parallel surface mountings, the parallel surface mountingsinclude mutually facing surfaces which lie in parallel planes which areperpendicular to an optical axis of a light beam propagating from thelaser diode light source towards the modulator via the lens.

Preferably the laser diode light source and the modulator are aligned byrelative movement thereof in the parallel planes and are fixed indesired alignment by fixing the mutually facing surfaces together.

Further in accordance with a preferred embodiment of the presentinvention at least one of the laser diode light source and the modulatorare mounted onto a support element by means of side mounting blockswhich are fixed in position upon precise mutual alignment of the laserdiode light source and the modulator.

Preferably the modulator is implemented in gallium arsenide.

There is also provided in accordance with a preferred embodiment of thepresent invention a method of producing a modulated light sourceincluding the steps of providing lator, fiberlessly coupling a laserdiode light source to the modulator, and enclosing the modulator and thelaser diode light source within a housing together with output opticsoperative to direct modulated light from the modulator into an opticalfiber extending outwardly from the housing.

Further in accordance with a preferred embodiment of the presentinvention the step of fiberlessly coupling a laser diode light source tothe modulator includes the steps of using at least one externalmanipulator, manipulating at least one of the modulator and the laserdiode light source relative to the other such that the output beam ofthe laser diode enters the modulator with relatively low light loss, andfixing the modulator and the laser diode light source in desiredrelative positions independently of the external manipulator, anddisengaging the at least one external manipulator from the modulatedlight source.

Still further in accordance with a preferred embodiment of the presentinvention the step of fixing the modulator and the laser diode lightsource in desired relative positions comprises fixedly attachingparallel surfaces attached to the modulator and to the laser diode lightsource to each other in desired relative orientations.

Preferably the step of fixing the modulator and the laser diode lightsource in desired relative positions includes employing side mountingblocks to fix at least one of the laser diode light source and themodulator in position upon precise mutual alignment of the laser diodelight source and the modulator.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully fromthe following detailed description, taken in conjunction with thedrawings in which:

FIG. 1A is a simplified sectional illustration of a modulated lightsource module constructed and operative in accordance with a preferredembodiment of the present invention;

FIG. 1B is a simplified sectional illustration of a modulated lightsource module constructed and operative in accordance with anotherpreferred embodiment of the present invention;

FIGS. 2A and 2B are simplified, partially cut-away pictorialillustrations of alignment and fixing of a Mach-Zehnder type modulatorand a laser diode light source arranged in a housing in the manner shownin FIG. 1A in accordance with one embodiment of the present invention;and

FIGS. 3A and 3B are simplified, partially cut-away pictorialillustrations of alignment and fixing of a Mach-Zehnder type modulatorand a laser diode light source arranged in a housing in the manner shownin FIG. 1B in accordance with one embodiment of the present invention;

FIGS. 4A, 4B, 4C, 4D & 4E are simplified pictorial illustrations ofvarious steps in the alignment and fixing of a Mach-Zehnder typemodulator and a laser diode light source arranged in a housing inaccordance with another embodiment of the present invention; and

FIGS. 5A, 5B, 5C, 5D & 5E are simplified pictorial illustrations ofvarious steps in the alignment and fixing of a Mach-Zehnder typemodulator and a laser diode light source arranged in a housing inaccordance with yet another embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference is now made to FIG. 1A, which is a simplified sectionalillustration of a modulated light source module constructed andoperative in accordance with a preferred embodiment of the presentinvention.

The modulated light source of FIG. 1A Preferably comprises a generallycylindrical housing 10, typically having a rectangular cross section andpreferably having mounting surfaces, such as end flanges 12 and 14 atrespective opposite ends thereof. Housing 10 is typically formed ofmetal, but may be formed of any suitable material, such as a plasticmaterial.

A laser diode light source assembly 16 is mounted at one end of housing10 and secured thereto at flange 12. Typically the laser diode lightsource assembly 16 comprises a base element 18, which is attached toflange 12. A laser diode 20, typically an 1310 nm or 1550 nm laserdiode, is mounted on base element 18 and arranged to direct a beam oflaser radiation along an optical axis 22, which is preferably coaxialwith the longitudinal axis of cylindrical housing 10.

The laser diode 20 typically receives electrical power and controlinputs from an external driver (not shown). A lens 24 is preferablymounted on an internal mounting cylinder 26, fixed to base element 18and is located within housing 10 for receiving the beam of laserradiation from laser diode 20 and directing it onto an radiation inputlocation 28 in a modulator assembly 30.

Alternatively the internal mounting cylinder 26 may also be fixed to thehousing 10 instead of being fixed to the base element 18.

It is a particular feature of the present invention that the opticalconnection between the laser diode 20 and the modulator assembly 30 is afiberless connection. This feature greatly simplifies manufacture of themodulated light source and provides much more efficient coupling betweenthe laser diode 20 and the modulator assembly 30 than was possible inthe prior art which employs fiber connections.

The modulator assembly 30 is preferably a Mach-Zehnder type modulator,although any other suitable type of modulator can be employed. Modulatorassembly 30 preferably comprises a substrate 32, preferably GalliumArsenide (GaAs), onto which is formed, preferably by conventionalsemiconductor fabrication techniques, an input waveguide 34 which leadsto a splitter 36.

A pair of generally parallel waveguides 38 and 40 extend from splitter36 to a combiner 42 which terminates in an output waveguide 44.Radiation input location 28 is preferably at an end of input waveguide34.

Output waveguide 44 preferably defines a radiation output location 48which provides a modulated beam which can be coupled to an output fiber50 by any suitable pigtailing technique. One such pigtailing techniqueemploys the structure shown in FIG. 1A, namely a fiber mounting assembly52 which includes a base element 54 onto which is mounted a fibersupport 56. Base element 54 is preferably mounted onto flange 14 andalso includes a lens 58, which is mounted via an internal mountingcylinder 60, fixed to base element 54. Lens 58 preferably directs lightfrom radiation output location 48 onto an end of fiber 50 mounted onfiber support 56.

Alternatively the lens 58 does not have to be part of the fiber mountingassembly 52, rather the internal mounting cylinder 60 may be fixeddirectly to the housing 10 instead of being fixed to the base element54.

It is appreciated that alternatively input and output waveguides 34 and44 may be obviated. In such a case, light is directed directly to andfrom the splitter 36 and the combiner 42 respectively.

Modulator 30, which is typically a Mach-Zehnder modulator as shown inFIG. 1A, preferably includes multiple signal inputs 62 which supplysuitable electrical signals from an external signal source (not shown)to waveguides 38 and 40 for varying the relative phase of the radiationpassing therethrough, thereby to modulate the output intensity byradiation interference in the combiner 42 in a known manner.

Reference is now made to FIG. 1B, which is a simplified sectionalillustration of a modulated light source module constructed andoperative in accordance with another preferred embodiment of the presentinvention.

The modulated light source of FIG. 1B preferably comprises a generallycylindrical housing 110, typically having a rectangular cross sectionand preferably having mounting surfaces, such as end flanges 112 and 114at respective opposite ends thereof. Housing 110 is typically formed ofmetal, but may be formed of any suitable material, such as a plasticmaterial.

A laser diode light source assembly 116 is mounted at one end of housing110 and secured thereto at flange 112. Typically the laser diode lightsource assembly 116 comprises a base element 118, which is attached toflange 112. A laser diode 120, typically an 1310 nm or 1550 nm laserdiode, is mounted on base element 118 and arranged to direct a beam oflaser radiation directly to a radiation input location 128 of amodulator 130 which is butted against laser diode 120.

The laser diode 120 typically receives electrical power and controlinputs from an external driver (not shown).

As noted above, it is a particular feature of the present invention thatthe optical connection between the laser diode 120 and the modulatorassembly 130 is a fiberless connection, such as in this example, abutted optical connection. This feature greatly simplifies manufactureof the modulated light source and provides much more efficient couplingbetween the laser diode 120 and the modulator assembly 130 than waspossible in the prior art which employs fiber connections.

The modulator assembly 130 is preferably a Mach-Zehnder type modulator,although any other suitable type of modulator can be employed. Modulatorassembly 130 preferably comprises a substrate 132, preferably GalliumArsenide (GaAs), onto which is formed, preferably by conventionalsemiconductor fabrication techniques, an input waveguide 134 which leadsto a splitter 136.

A pair of generally parallel waveguides 138 and 140 extend from splitter136 to a combiner 142 which terminates in an output waveguide 144.Radiation input location 128 is preferably at an end of input waveguide134.

Output waveguide 144 preferably defines a radiation output location 148which provides a modulated beam which can be coupled to an output fiber150 by any suitable pigtailing technique. One such pigtailing techniqueemploys the structure shown in FIG. 1B, namely a fiber mounting assembly152 which includes a base element 154 onto which is mounted a fibersupport 156. Base element 154 is preferably mounted onto flange 114 andalso includes a lens 158, which is mounted via an internal mountingcylinder 160, fixed to base element 154. Lens 158 preferably directslight from radiation output location 148 onto an end of fiber 150mounted on fiber support 156.

It is appreciated that alternatively input and output waveguides 134 and144 may be obviated. In such a case, light is directed directly to andfrom the splitter 136 and the combiner 142 respectively.

Modulator 130, which is typically a Mach-Zehnder modulator as shown inFIG. 1B, preferably includes multiple signal inputs 162 which supplysuitable electrical signals from an external signal source (not shown)to waveguides 138 and 140 for varying the relative phase of theradiation passing therethrough, thereby to modulate the output intensityby radiation interference in the combiner 142 in a known manner.

Reference is now made to FIGS. 2A and 2B, which are simplified,partially cut-away pictorial illustrations of alignment and fixing of aMach-Zehnder type modulator and a laser diode light source in a housingin accordance with one embodiment of the present invention. For the sakeof clarity and conciseness, all of the structural elements of themodulated light source appearing in FIGS. 2A and 2B are identified bythe corresponding reference numerals used to designate them in FIG. 1A.

FIG. 2A shows that the laser diode light source assembly 16 has multipledegrees of freedom in positioning relative to flange 12. The relativepositioning show in FIG. 2A is seen to be less than optimal, in that theradiation output of laser diode 20 is being focussed by lens 24 onto alocation 200 which is offset from the radiation input location 28defined on input waveguide 34. FIG. 2B illustrates that by suitablerepositioning of base element 18 of assembly 16 relative to flange 12,location 200 is caused to be at the radiation input location 28, asdesired and a desired rotational orientation of the laser diode isprovided so that a desired orientation of the polarization of the beamis realized.

When the relative positions of the laser diode light source assembly 16and flange 12 are as shown in FIG. 2B, the base element 18 is preferablybonded onto flange 12, preferably using a thin layer of UV curableadhesive 204 which does not involve significant shrinkage during curing,as by use of a UV light source 202, so that the relative position shownin FIG. 2B is preserved. Alternatively, any other suitable fixingtechnique or technology may be employed, such as, for example, laserwelding or soldering.

Reference is now made to FIGS. 3A and 3B, which are simplified,partially cut-away pictorial illustrations of alignment and fixing of aMach-Zehnder type modulator and a laser diode light source in a housingin accordance with another embodiment of the present invention. It isnoted that the methodology of FIGS. 3A and 3B is generally identical tothat of FIGS. 2A and 2B, notwithstanding that FIGS. 2A and 2B relate tothe structure of FIG. 1A while FIGS. 3A and 3B relate to the structureof FIG. 1B.

For the sake of clarity and conciseness, all of the structural elementsof the modulated light source appearing in FIGS. 3A and 3B areidentified by the corresponding reference numerals used to designatethem in FIG. 1B.

FIG. 3A shows that the laser diode light source assembly 116 hasmultiple degrees of freedom in positioning relative to flange 112. Therelative positioning show in FIG. 3A is seen to be less than optimal, inthat the radiation output of laser diode 120 is located at a location300 which is offset from the radiation input location 128 defined oninput waveguide 134. FIG. 3B illustrates that by suitable repositioningof base element 118 of assembly 116 relative to flange 112, location 300is caused to be at the radiation input location 128, as desired and adesired rotational orientation of the laser diode is provided so that adesired orientation of the polarization of the laser diode radiation isrealized.

When the relative positions of the laser diode light source assembly 116and flange 112 are as shown in FIG. 3B, the base element 118 ispreferably bonded onto flange 112, preferably using a thin layer of UVcurable adhesive 304 which does not involve significant shrinkage duringcuring, as by use of a UV light source 302, so that the relativeposition shown in FIG. 3B is preserved. Alternatively, any othersuitable fixing technique or technology may be employed, such as, forexample, laser welding or soldering.

Reference is now made to FIGS. 4A, 4B, 4C, 4D & 4E, which are simplifiedillustrations of various steps in the alignment and fixing of aMach-Zehnder type modulator and a laser diode light source in a housingin accordance with another embodiment of the present invention.

In the embodiment of FIGS. 4A-4E, there is shown a preferred techniquefor precise alignment and assembly of a modulated light source includinga modulator assembly 430, which preferably comprises a substrate 432,preferably Gallium Arsenide (GaAs), onto which is formed, preferably byconventional semiconductor fabrication techniques, an input waveguide434 which leads to a splitter 436.

As seen in FIG. 4A, a pair of generally parallel waveguides 438 and 440extend from splitter 436 to a combiner 442 which terminates in an outputwaveguide 444. Radiation input location 428 is preferably at an end ofinput waveguide 434.

Output waveguide 444 preferably defines a radiation output location 448which provides a modulated beam which can be coupled to an output fiber(not shown) by any suitable pigtailing technique. One such pigtailingtechnique employs the structure shown in FIG. 1A, namely a fibermounting assembly 52 which includes a base element 54 onto which ismounted a fiber support 56. It is appreciated that, alternatively, inputand output waveguides 434 and 444 may be obviated. In such a case, lightis directed directly to and from the splitter 436 and the combiner 442respectively.

Modulator 430, which is typically a Mach-Zehnder modulator as shown inFIG. 1A, preferably is provided with multiple signal inputs (not shown)supply suitable electrical signals from an external signal source (notshown) to waveguides 438 and 440 for varying the relative phase of theradiation passing therethrough, thereby to modulate the output intensityby radiation interference in the combiner 442 in a known manner.

An input lens 450 is preferably precisely mounted onto a substrate 452,typically formed of glass, ceramic or any other suitable material, andwhich also supports substrate 432.

As seen in FIG. 4A, a laser diode light source assembly 466, typicallycomprises a base element 468, which is supported during assembly as by avacuum holder 470 for selectable positioning with multiple degrees offreedom relative to substrate 452. A laser diode 472, typically an 1310nm or 1550 nm laser diode, is fixedly mounted to base element 468.

As seen in FIG. 4B, the laser diode light source assembly 466 isprecisely positioned so as to direct a beam of laser radiation via lens450 onto radiation input location 428 of modulator 430 and such that adesired rotational orientation of the laser diode is provided so that adesired orientation of the polarization of the beam is realized. Thelaser diode 472 typically receives electrical power and control inputsfrom an external driver (not shown).

As noted above, it is a particular feature of the present invention thatthe optical connection between the laser diode 472 and the modulatorassembly 430 is a fiberless connection. This feature greatly simplifiesmanufacture of the modulated light source and provides much moreefficient coupling between the laser diode 472 and the modulatorassembly 430 than was possible in the prior art which employs fiberconnections.

Once desired positioning of the laser diode light source assembly 466has been achieved, side mounting blocks 480 and 482 are carefullypositioned alongside base element 468 (FIG. 4C) and are bonded theretoand to substrate 452, preferably using a thin layer of UV curableadhesive (not shown) which does not involve significant shrinkage duringcuring, as by use of a UV light source 402, so that the relativeposition shown in FIG. 4C is preserved, as seen in FIG. 4D.

The finished, suitably aligned modulated light source is shown in FIG.4E.

Reference is now made to FIGS. 5A, 5B, 5C, 5D & 5E, which are simplifiedillustrations of various steps in the alignment and fixing of aMach-Zehnder type modulator and a laser diode light source in a housingin accordance with yet another embodiment of the present invention.

In the embodiment of FIGS. 5A-5E, there is shown a preferred techniquefor precise alignment and assembly of a modulated light source includinga modulator assembly 530, which preferably comprises a substrate 532,preferably Gallium Arsenide (GaAs), onto which is formed, preferably byconventional semiconductor fabrication techniques, an input waveguide534 which leads to a splitter 536.

As seen in FIG. 5A, a pair of generally parallel waveguides 538 and 540extend from splitter 536 to a combiner 542 which terminates in an outputwaveguide 544. Radiation input location 528 is preferably at an end ofinput waveguide 534.

Output waveguide 544 preferably defines a radiation output location 548which provides a modulated beam which can be coupled to an output fiber(not shown) by any suitable pigtailing technique. One such pigtailingtechnique employs the structure shown in FIG. 1B, namely a fibermounting assembly 152 which includes a base element 154 onto which ismounted a fiber support 156. It is appreciated that, alternatively,input and output waveguides 534 and 544 may be obviated. In such a case,light is directed directly to and from the splitter 536 and the combiner542 respectively.

Modulator 530, which is typically a Mach-Zehnder modulator as shown inFIG. 1B, preferably is provided with multiple signal inputs (not shown)supply suitable electrical signals from an external signal source (notshown) to waveguides 538 and 540 for varying the relative phase of theradiation passing therethrough, thereby to modulate the output intensityby radiation interference in the combiner 542 in a known manner. Asubstrate 550, typically formed of glass, ceramic or any other suitablematerial supports substrate 532.

As seen in FIG. 5A, a laser diode light source assembly 566, typicallycomprises a base element 568, which is supported during assembly as by avacuum holder 570 for selectable positioning with multiple degrees offreedom relative to substrate 532. A laser diode 572, typically an 1310nm or 1550 nm laser diode, is fixedly mounted to base element 568.

As seen in FIG. 5B, the laser diode light source assembly 566 isprecisely positioned so as to direct a beam of laser radiation directlyto a radiation input location 528 of modulator 530 which is buttedagainst laser diode 570 and such that a desired rotational orientationof the laser diode is provided so that a desired orientation of thepolarization of the laser diode radiation is realized. The laser diode572 typically receives electrical power and control inputs from anexternal driver (not shown).

As noted above, it is a particular feature of the present invention thatthe optical connection between the laser diode 572 and the modulatorassembly 530 is a fiberless connection. This feature greatly simplifiesmanufacture of the modulated light source and provides much moreefficient coupling between the laser diode 572 and the modulatorassembly 530 than was possible in the prior art which employs fiberconnections.

Once desired positioning of the laser diode light source assembly 566has been achieved, side mounting blocks 580 and 582 are carefullypositioned alongside base element 568 and are bonded thereto and tosubstrate 552 (FIG. 5C), preferably using a thin layer of UV curableadhesive (not shown) which does not involve significant shrinkage duringcuring, as by use of a UV light source 502, so that the relativeposition shown in FIG. 5B is preserved, as seen in FIG. 5D.

The finished, suitably aligned modulated light source is shown in FIG.5E.

It will be appreciated by persons skilled in the art that the presentinvention is not limited by what has been particularly shown anddescribed hereinabove. The present invention also includes combinationsand subcombinations of the various features described hereinabove aswell as modifications and variations thereof as would occur to a personof ordinary skill in the art upon reading the foregoing description andwhich are not in the prior art.

What is claimed is:
 1. A light source module comprising: a first waveguide device, implemented in gallium arsenide, disposed in a housing; a second waveguide device disposed in said housing and being operative whereby light from said second waveguide device is fiberlessly coupled to said first waveguide device, said second waveguide device being a discrete element which is mechanically mounted in a desired position with respect to said first waveguide device; and output optics operative to direct light from the first waveguide device into an optical fiber extending outwardly from said housing; wherein light from said second waveguide device is coupled to an input to said first waveguide device via a discrete lens.
 2. A light source according to claim 1 and wherein said first waveguide device comprises: an input multi-mode interference coupler; an output multi-mode interference coupler; and first and second waveguides interconnecting said input multi-mode interference coupler and said output multi-mode interference coupler, said first and second waveguides having associated therewith electrodes for the application of voltage thereacross, thereby to vary the phase of light passing therealong.
 3. A light source according to claim 1 and wherein said first waveguide device comprises: an input Y-junction splitter; an output Y-junction combiner; and first and second waveguides interconnecting said Y-junction splitter and said output Y-junction combiner, said first and second waveguides having associated therewith electrodes for the application of voltage thereacross, thereby to vary the phase of light passing therealong.
 4. A light source according to claim 1 wherein each of said second waveguide device and said first waveguide device are mounted on parallel surface mountings, said parallel surface mountings include mutually facing surfaces which lie in parallel planes which are perpendicular to an optical axis of a light beam propagating from said second waveguide device towards said first waveguide device.
 5. A light source according to claim 1 and wherein said second waveguide device and said first waveguide device are aligned by relative movement thereof in said parallel planes and are fixed in desired alignment by fixing said mutually facing surfaces together.
 6. A light source according to claim 1 and wherein each of said second waveguide device and said first waveguide device are mounted on parallel surface mountings, said parallel surface mountings include mutually facing surfaces which lie in parallel planes which are perpendicular to an optical axis of a light beam propagating from said second waveguide device towards said first waveguide device via said lens.
 7. A light source according to claim 1 and wherein at least one of said second waveguide device and said first waveguide device are mounted onto a support element by means of side mounting blocks which are fixed in position upon precise mutual alignment of said second waveguide device and said first waveguide device. 